Aircraft, particularly military aircraft, often utilize racks located beneath their wings and/or fuselages to carry stores and to release such stores from the aircraft upon command. The stores typically are munitions such as bombs, missiles, and rockets, but also include other items such as fuel tanks.
Typical store racks are shown in U.S. Pat. Nos. 4,043,525 and 4,347,777, which are incorporated herein by reference, in their entireties. As is well known, store racks typically include a release mechanism for selectively releasing a store from the aircraft upon command and often include one or more ejector rams for forcibly ejecting stores from the aircraft during their release. It is also known that various means can be used for actuating the release mechanisms and/or the ejector rams. Such means may include compressed springs, pyrotechnic cartridges, hydraulic systems, and pneumatic systems. Additionally, the release mechanisms and the ejector rams of any given store rack may be actuated via the same source of power or via separate unrelated sources of power.
The present invention pertains particularly to pneumatically actuated store racks, which have increasingly been utilized for supplying the power to the ejector rams to forcibly eject stores. Pneumatically actuated systems have several advantages including low weight, high reliability, low maintenance requirements, and operational safety.
Typically, compressed gas is supplied to a pneumatically actuated ejection system via a compressed gas storage system that, during flight and prior to the release of a store, maintains the compressed gas at a pressure sufficient to properly operate the ejection system. Because of this, several issues are of concern when utilizing pneumatically actuated ejection systems. In particular, throughout the flight of an aircraft, the gas storage system may vary in temperature by as much as over 200 degrees Fahrenheit. Such temperature variances can cause substantial changes in the pressure of the compressed gas stored in the gas storage system. This is a problem because, in many cases, the pneumatically actuated ejection systems are configured to be operated using compressed gas within fairly narrow and specific pressure ranges. As such, numerous methods have been developed and utilized to ensure that the gas stored in the gas storage system is maintained within the proper operating pressure range of the ejection system. One such method is to utilize an on-board heat source for heating the compressed gas within the gas storage system so as to increase the pressure of the compressed gas as needed. Another method is to provide an on-board gas compressor for adding additional compressed gas to the gas storage system to thereby increase the pressure of the stored gas as needed. It is also known to utilize vent valves to decrease the pressure of the stored gas as needed.
Despite the various developments and improvements associated with pneumatically actuated store rack ejection systems, there nonetheless remains room for further improvement.
The present invention eliminates many of the concerns associated with prior art ejection systems by providing a method of supplying the gas storage system with compressed gas that has a pressure-to-temperature ratio that ensures proper jettisoning of stores under all design temperature specifications, without the need for on-board compressors, heating elements, or venting systems. The invention can be practiced by simply making a temperature measurement, during or before a step of supplying the gas storage system with compressed gas, and determining therefrom the necessary pressure of compressed gas to initially supply to the gas storage system. By so doing, the performance of the ejection system at various temperatures is automatically controlled, regardless of the temperature of the compressed gas immediately after such gas is supplied to the gas storage system.
In general, a first method of practicing the invention comprises the step of providing an aircraft having at least one pneumatically actuated store rack and a gas storage system. The first method also comprises attaching a store to the store rack, predicting a minimum operational temperature of compressed gas within the gas storage system that is likely to occur during flight of the aircraft, and predicting a maximum operational temperature of compressed gas within the gas storage system that is likely to occur during flight of the aircraft. Yet further, the first method comprises the step of calculating a pressure-to-temperature ratio that ensures that an amount of compressed gas stored within the gas storage system will maintain a pressure sufficient to actuate the store rack in a manner to safely and effectively jettison the store from the aircraft, regardless of whether such an amount of compressed gas is at the minimum operational temperature or the maximum operational temperature. Finally, the first method yet further comprises the steps of supplying compressed gas to the gas storage system in a manner such that the gas storage system contains an amount of compressed gas at approximately the calculated pressure-to-temperature ratio, and using the amount of compressed gas to actuate the store rack and thereby jettison the store from the aircraft.
A second method of practicing the invention comprises providing a similar aircraft and attaching a store to the store rack. This method further includes determining an initial pressure for supplying the gas storage system with compressed gas. In this method, the determination of the initial pressure is dependent upon a temperature measurement. Finally, this method further comprises the steps of supplying compressed gas to the gas storage system in a manner such that an amount of compressed gas within the gas storage system has a pressure approximately equal to the determined initial pressure, and using the portion of the amount of compressed gas to actuate the store rack and thereby jettison the store from the aircraft.
A third method of practicing the invention, once again, comprises providing a similar aircraft and attaching a store to the store rack. This method further includes calculating a pressure-to-temperature ratio and supplying compressed gas to the gas storage system in a manner such that an amount of compressed gas within the gas storage system has a pressure-to-temperature ratio approximately equal to the calculated pressure-to-temperature ratio. In this method, the calculated pressure-to-temperature ratio is such that the amount of compressed gas would have a pressure capable of actuating the store rack in a manner to impart at least a first total amount of work to the store when the store is released from the aircraft and when the amount of compressed gas is at a temperature of minus forty degrees Fahrenheit. Similarly, the calculated pressure-to-temperature ratio is also such that the amount of compressed gas would have a pressure low enough to actuate the store rack in a manner to impart at most a second total amount of work to the store when the store is released from the aircraft and when the amount of compressed gas is at a temperature of one hundred and sixty-five degrees Fahrenheit. The second total amount of work is at most 1.5 times greater than the first total amount of work. With the temperature of the compressed gas varying between one hundred and sixty-five degrees and minus forty degrees, the ejection system will impart a range of amounts of work to a store during its release. However, by virtue of the calculated pressure-to-temperature ratio, the ejection velocity will vary by only plus or minus ten percent. Finally, the method yet further comprises using the amount of compressed gas to actuate the store rack and thereby jettison the store from the aircraft.